This invention relates to new and useful improvements in fasteners and particularly is concerned with fasteners of the type that are installed by a power tool and with a portion thereof broken off by the tool after installation.
Fasteners, referred to as lock bolts in the trade, have heretofore been used which are installed by a special power tool. More particularly, such lock bolts include a headed shank having circumferential parallel grooves for receiving a collar to be swaged or crimped thereon and also having circumferential parallel grooves on a tail portion thereof arranged for engagement by the power tool capable of pulling parts together that are to be connected, then swaging the collar to secure it on the grooved portion, and then breaking off the tail portion of the shank. One advantage of these lock bolts is that they provide rapid assembly. Also, the clamping force can be specifically controlled and not be dependent upon the skill of a tool operator. Furthermore, these fasteners are vibration resistant and can be readily inspected to determine that a joint is properly assembled.
These prior lock bolts, however, have some disadvantages. One main disadvantage is that they are not readily removable. That is, the only manner of removing them is by shearing off the head of the shank or shearing off the collar, drilling them out, or burning them out with a torch.
Another disadvantage of lock bolts now in use is that they cannot be checked or tightened if loosening occurs in service and furthermore they are not reusable in any form.